The present invention relates generally to leads for conducting electrical signals to and from the heart. More particularly, it pertains to a ring electrode for pacing electrical signals from the heart.
Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmias, or to stimulate contraction of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle. Technically, the pacemaker or the automatic implantable cardioverter defibrillator (AICD) receives signals from the lead and interprets them. In response to these signals the pacemaker can pace or not pace. The AICD can pace, not pace or shock, and not shock. In response to a sensed bradycardia or tachycardia condition, a pulse generator produces pacing or defibrillation pulses to correct the condition. The same lead used to sense the condition is sometimes also used in the process of delivering a corrective pulse or signal from the pulse generator of the pacemaker.
Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the ventricular epicardium. Most commonly, permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. The lead may also be positioned in both chambers, depending on the lead, as when a lead passes through the atrium to the ventricle. sense electrodes may be positioned within the atrium or the ventricle of the heart. For pacing applications, the lead may be positioned in cardiac veins or arteries.
Positioning an electrode disposed on a distal end of a lead within a vein or artery presents additional challenges in maintaining the lead in a fixed position since the distal end of the lead does not abut a surface. These challenges also may result in poor pacing and sensing capabilities of the electrode.
Therefore, there is a need for a lead having an electrode for positioning within cardiac veins, or arteries that allows for fixation therein. In addition, what is needed is a lead which provides desirable pacing and sensing properties.
A body-implantable lead assembly includes a lead, one end being adapted to be connected to electrical supply for providing or receiving electrical pulses. The lead extends to a distal end which is adapted to be connected to tissue of a living body. The lead also has a sheath of material inert to body materials and fluids and at least one conductor extending through the lead body.
The distal end of the lead assembly is adapted for implantation proximate to or within the heart while connected with a system for monitoring or stimulating cardiac activity. In addition, the distal end of the lead assembly is implanted in cardiac veins or arteries, depending on the application. The distal end includes a ring electrode electrically coupled with a first porous member electrically coupled with the ring electrode. A conductor coil is disposed within the lead body and is electrically coupled with the ring electrode.
In one embodiment, the ring electrode includes a cut out, and the first porous member is disposed in the cut out. The first porous member is electrically active, and paces and/or senses the tissue once it is implanted. In addition, the surface area of the first porous member is changed to control electrically properties of the lead assembly. The first porous member is formed of a material which is inert to a living body.
The first porous member, in another embodiment, includes a mesh screen. The mesh screen is formed of various materials, including, but not limited to, platinum iridium, iridium oxide, titanium nitride, titanium oxide, diamond, tantalum. In another embodiment, the first porous member is sputter coated on the ring electrode with liquid metal. In yet another embodiment, the first porous member is formed by etching the ring electrode with acid. The first porous member, in one embodiment, is formed by laser scribing the ring electrode. In another embodiment, the first porous member is formed by particle blasting the ring electrode. In yet another embodiment, the first porous member is formed by chemical vapor deposition of the ring electrode. The first porous member, in another embodiment, is formed by coating the ring electrode with diamond.
In another embodiment, a ring electrode is electrically coupled with the conductor and a first porous member electrically coupled with the ring electrode. A second porous member is disposed over the first porous member, and each is electrically coupled with the ring electrode. The second porous member is bonded with the ring electrode, for instance, by sintering or welding. The first porous member and the second porous member are electrically active, and can pace and/or sense the tissue once it is implanted.
The above-described lead assembly provides several benefits including increased sensing and pacing properties. Furthermore, the first and/or second porous members will assist in retaining the electrode assembly in a desired location due to the tissue ingrowth.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents.